chore(release): prepare 1.15.0 - #161

Summary

• bump bailian-cli-core, bailian-cli-runtime, bailian-cli-commands, bailian-cli, and knowledge-studio-cli from 1.14.3 to 1.15.0
• synchronize all first-party Bailian Skill metadata.version fields to 1.15.0
• complete the version metadata required for the existing 1.15.0 changelog entry and stable Publish workflow

Validation

• pnpm run sync:skill-assets
• vp check (0 errors; 5 pre-existing warnings outside this diff)
• CI=true node tools/release/publish-channel.mjs --channel test --knowledge --dry-run
  • generated references matched
  • all five packages built and packed
  • publint passed for all five packages
  • gitleaks found no leaks
• git diff --check